Hello Greg,
Thank you for your feedback.
Subject: Re: [PATCH] time: Fix CLOCK_MONOTONIC_RAW sub-nanosecond accounting
On Mon, May 21, 2018 at 06:57:26PM +0100, Fabrizio Castro wrote:
From: John Stultz john.stultz@linaro.org
commit 3d88d56c5873f6eebe23e05c3da701960146b801 upstream.
Due to how the MONOTONIC_RAW accumulation logic was handled, there is the potential for a 1ns discontinuity when we do accumulations. This small discontinuity has for the most part gone un-noticed, but since ARM64 enabled CLOCK_MONOTONIC_RAW in their vDSO clock_gettime implementation, we've seen failures with the inconsistency-check test in kselftest.
This patch addresses the issue by using the same sub-ns accumulation handling that CLOCK_MONOTONIC uses, which avoids the issue for in-kernel users.
Since the ARM64 vDSO implementation has its own clock_gettime calculation logic, this patch reduces the frequency of errors, but failures are still seen. The ARM64 vDSO will need to be updated to include the sub-nanosecond xtime_nsec values in its calculation for this issue to be completely fixed.
Signed-off-by: John Stultz john.stultz@linaro.org Tested-by: Daniel Mentz danielmentz@google.com Cc: Prarit Bhargava prarit@redhat.com Cc: Kevin Brodsky kevin.brodsky@arm.com Cc: Richard Cochran richardcochran@gmail.com Cc: Stephen Boyd stephen.boyd@linaro.org Cc: Will Deacon will.deacon@arm.com Cc: "stable #4 . 8+" stable@vger.kernel.org Cc: Miroslav Lichvar mlichvar@redhat.com Link: http://lkml.kernel.org/r/1496965462-20003-3-git-send-email-john.stultz@linar... Signed-off-by: Thomas Gleixner tglx@linutronix.de [fabrizio: cherry-pick to 4.4. Kept cycle_t type for function logarithmic_accumulation local variable "interval". Dropped casting of "interval" variable] Signed-off-by: Fabrizio Castro fabrizio.castro@bp.renesas.com Signed-off-by: Biju Das biju.das@bp.renesas.com
Hello Greg,
we noticed tools/testing/selftests/timers/clocksource-switch.c was failing for us, this patch fixes the cause of the failure. Are you happy to take this patch?
For what kernel tree(s)?
4.4.y
And why did you not cc: the developers and maintainer of this subsystem?
Sorry, I wasn't sure about bothering the other developers with this. I'll repost with all the relevant people in cc.
Thanks, Fab
thanks,
greg k-h
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